Pharmaceutical compositions and methods to vaccinate against candidiasis

ABSTRACT

A  Candida albicans  bloodstream infections cause significant morbidity and mortality in hospitalized patients. Filament formation and adherence to host cells are critical virulence factors of  C. albicans . Multiple filamentation regulatory pathways have been discovered, however the downstream effectors of these regulatory pathways remain unknown. The cell surface proteins in the ALS group are downstream effectors of the filamentation regulatory pathway. Particularly, Als1p mediates adherence to endothelial cells in vitro and is required for virulence. The blocking of adherence by the organism is described resulting from the use of a composition and method disclosed herein. Specifically, a pharmaceutical composition comprised of a gene, gene product, or specific antibody to the ALS gene family is administered as a vaccine to generate an immune response capable of blocking adherence of the organism.

RELATED INFORMATION

This application is a divisional application of U.S. Ser. No. 10/245,802, filed Sep. 13, 2002, now U.S. Pat. No. 8,541,008. The priority of the prior application is expressly claimed, and the disclosure of the prior application is hereby incorporated in its entirety.

STATEMENT AS TO FEDERALLY SPONSORED RESEARCH

This invention was made with Government support under Public Health Service grants PO-1Al-37194, RO1A1-19990, and MO1 RR0425. The Government has certain rights in this invention.

FIELD OF INVENTION

This invention relates to Candida albicans surface adhesin proteins, to antibodies resulting from an immune response to vaccination, to compositions used as prophylactic or therapeutic vaccines, and to methods for the prevention and/or treatment of candidiasis.

BACKGROUND OF INVENTION

A dramatic increase in the incidence of nosocomial infections caused by Candida species has been observed in recent years. The incidence of hematogenously disseminated candidal infections increased 11-fold from 1980 to 1989. This increasing incidence has continued through the 1990s and into the 2000s. Infections by Candida species are now the fourth most common cause of nosocomial septicemia, are equal to that of Escherichia coli, and surpass the incidence caused by Klebsiella species. Furthermore, Candida species are the most common cause of deep-seated fungal infections in patients who have extensive burns. Up to 11% of individuals undergoing bone marrow transplantation and 13% of those having an orthotopic liver transplant will develop an invasive candidal infection.

C. albicans infections are difficult to diagnose and the organism can survive in vivo without causing overtly detectable disease symptoms and can cause overt disease symptoms that vary in site and in severity. The infection can be localized and superficial or systemic and disseminated. C. albicans possesses numerous mechanisms to adapt to host sites, and differential gene expression under these mechanisms. Candida albicans can switch between two morphologies: the blastospore (budding yeast) and filamentous (hyphae and pseudohyphae) phases. Candida mutants that are defective in genes regulating filamentation are reported to have reduced virulence in animal models. This reduced virulence suggests that the ability to change from a blastospore to a filament is a key virulence factor of C. albicans. To date, no essential effectors of these filamentation pathways have been identified in C. albicans. See Caesar-TonThat, T. C. and J. E. Cutler, “A monoclonal antibody to Candida albicans enhances mouse neutrophil candidacidal activity,” Infect. Immun. 65:5354-5357, 1997.

The identification of effectors in the regulatory pathways of the organism that contribute to virulence offers the opportunity for therapeutic intervention with methods or compositions that are superior to existing antifungal agents. The identification of cell surface proteins that effect a regulatory pathway involved in virulence is particularly promising because characterization of the proteins enables immunotherapeutic techniques that are superior to existing antifungal agents when fighting a candidal infection. Also, both passive and active vaccination techniques offer unique prophylactic or therapeutic utilities depending on the clinical setting.

While potent antifungal agents exist that are microbicidal for Candida, the attributable mortality of candidemia is approximately 38%, even with treatment with potent anti-fungal agents such as amphotericin B. Also, existing agents such as amphotericin B tend to exhibit undesirable toxicity. Although additional antifungals may be developed that are less toxic than amphotericin B, it is unlikely that agents will be developed that are more potent. Therefore, either passive or active immunotherapy to treat or prevent disseminated candidiasis is a promising alternative to standard antifungal therapy.

The virulence of Candida albicans is regulated by several putative virulence factors, of which adherence to host constituents and the ability to transform from yeast-to-hyphae are among the most critical in determining pathogenicity. Adherent strains of C. albicans are more virulent than less-adhesive strains. Moreover, the more frequently isolated pathogenic species exhibit greater adhesive capacity. Investigations to understand C. albicans adhesion have involved characterization of the cell surface, since this is the initial point of contact between fungus and host. Moreover, filmentation pathways and their effect on molecules and pathways are implicated in virulence.

SUMMARY OF INVENTION

The present invention utilizes the gene, the family of gene products, a specific anisera of C. albicans agglutinin like sequence as a vaccine to treat, prevent, or alleviate disseminated candidiasis. The invention includes specially formulated compositions containing the ALS1a polynucleotides, the ALS1a polypeptides, monoclonal and polyclonal antisera specifically reactive with these molecules and compositions containing forms or derivatives of any of the foregoing molecules such as fragments or truncations. All of the compositions and methods of the invention take advantage of the role of the group of the ALS1 gene products in the adherence of the C. albicans to endothelial and epithelial cells and the role of ALS expression in adherence and filamentation and in the overall virulence of C. Albicans. Specifically, the control of ALS1 expression by transcription factor Efg1p, which is known to be a regulation of filamentation, demonstrates the susceptibility of the ALS1-expressed surface protein for use in therapeutic strategies, e.g. for use of the polypeptide as a vaccine to retard the pathogenesis of the organism, for use of antisera (polyclonal or monoclonal antibodies) in a passive immunization strategy, or for immunization by polynucleotide vaccination.

Pursuant to this invention, a member of the ALS gene family encodes a surface adhesin that is selected as the target of an immunotherapeutic strategy against Candida albicans. A demonstration that an expression product of an ALS gene has structural characteristics typical of surface proteins and is, in fact, expressed on the cell surface of C. albicans is a critical first criterion for any member of the group of proteins that acts as an adhesin to host tissues. For example, ALS1p has a signal peptide at the N-terminus, a glycosylphosphatidylinosine (GPI) anchorage sequence in the C-terminus, and a central region comprising repeats rich in threonine and serin. N—, and O— as well as several glycosylation sites, which is typical of proteins that are expressed on the cell surface. Indirect immunofluorescence using a monoclonal antibody directed against the N-terminus of Als1p revealed that Als1p is expressed during the log phase of blastospores. This expression of Als1p is increased during hyphal formation and is localized to the junction where the hyphal element extends from the blastospores as indicated by the diffused surface staining. Furthermore, a monoclonal antibody blocked the enhanced adherence of C. albicans overexpression mutant to endothelial cells, thereby establishing the principle for immunotherapy applications using members of the ALS family. The N-terminal region is a prime candidate for both passive and active immunization strategies and the gene and gene product can be used in a full length, truncated or modified form.

Additional evidence that ALS1p is a surface adhesin protein is based on data showing that antibodies that bind to the surface of C. albicans also bind to the surface of S. cerevisiae transformed with ALS1, but not with empty plasmid. The ALS1 protein also shares significant homology with the alpha-agglutinin of S. cerevisiae, which is expressed on the cell surface and mediates the binding of mating type alpha cells to mating type a cells. Moreover, expression of the ALS1 gene in S. cerevisiae increases the adherence of this organism to endothelial cells by approximately 100-fold. Because the ALS1 gene appears to encode a functional adhesin in Saccharomyes cerevisiae, it is certain that it also encodes a functional adhesin in C. albicans. The ALS1 gene was originally isolated by Hoyer et al. without a known function. Hoyer, L. L., S. Scherer, A. R. Shatzman, and G. P. Livi. 1995. Candida albicans ALM1: domains related to a Saccharonzyces cerevisiae sexual agglutinin separated the direct role of ALS1p in the various virulence pathways described herein, e.g. adherence, filamentation, and floculation satisfy a second criteria for use as a therapeutic agent, and lead to the therapeutic embodiments of the invention as described in greater detail below. Recognition of the unique characteristics of the ALS1 gene product in the pathogenesis of the organism suggests several discrete therapeutic approaches that interrupt critical virulence factors or pathways by a repeating motif. Mol. Microbiol. 15:39-54. (See also U.S. Pat. Nos. 5,668,263 and 5,817,466.)

In addition to the administration of anti-fungal agents, immunotherapeutic therapies enabled by the invention are employed to fight a fungal infection as part of an integrated anti-fungal clinical strategy that combines traditional anti-fungal agents with immunotherapeutics. Immunotherapeutics can be broadly defined in two categories: active and passive. Active immunotherapy relies on the administration of an antigenic compound as a vaccine that causes the body's immune system to mount an immune response to the compound. Typically, the immune response includes cell-mediated immune pathways and the generation of antibodies against the antigenic compound. In active immunization, antibodies specific for the compound and generated by the body also fight the fungal infection. Passive immunotherapy involves direct administration of the antibodies without the antigen. In passive immunization, the antibodies may be generated in vitro, such as in a conventional hybridoma or other expression system, and are administered directly to a patient. Both active and passive immunization offer the advantage of using antibodies that are highly specific and typically far less toxic than ordinary anti-fungal agents.

Although certain data and results presented herein are specific to the ALS1 species and related compounds, additional members of the ALS family exhibit similar functionality in the pertinent virulence pathways of Candida. The other members of the family, generally designated as ALS1-ALS1a share significant sequence homology with ALS1 and with each other and show highly conserved regions N terminal region. See FIG. 7. Thus, according to one aspect of the invention, a member of the ALS surface adhesin family of proteins or a fragment, conjugate, or analogue thereof, is formulated in a pharmaceutical composition and administered as a vaccine. ALS surface adhesin proteins are preferably obtained from Candida albicans, however, similar adhesin molecules or analogues or derivatives thereof may be of candidal origin and may be obtainable from strains belonging to the genera Candida such as Candida parapsilosis, Candida guilliermondii, Candida krusei, Candida dublinoensis, and Candida tropicalis. A surface adhesin protein according to the invention may be obtained in purified form, and thus, according to a preferred embodiment of the invention, a substantially pure ALS Candida albicans surface adhesin protein, or functional analogue, conjugate, or derivative thereof, is formulated as a vaccine to cause an immune response in a patient to block adhesion of the organism to the endothelial cells.

An analogue or derivative of the surface adhesion protein according to the invention may be identified and further characterized by the criteria described herein for the ALS gene and gene product. For example, a null mutant of the analogue or derivative would share markedly reduced adhesion to endothelial cells compared to controls. Similarly, over-expression of the analogue or derivative in an appropriate model would show an increased adherence to endothelial cells compared to controls and would be confirmed as a cell surface adhesin in accord with the criteria described above. Also, antisera to the analogue or derivative would cross-react with anti-ALS antibodies and would also exhibit increased survival times when administered in animal models of disseminated candidiasis as disclosed herein.

The present invention also provides an immunotherapeutic strategy against Candida infection at the level of binding to the vascular endothelial cells and through a downstream effector of the filamentation regulatory pathway. An immunotherapeutic strategy is uniquely advantageous in this context because: (i) the morbidity and mortality associated with hematogenously disseminated candidiasis remains unacceptably high, even with currently available antifungal therapy; (ii) a rising incidence of antifungal resistance is associated with the increasing use of antifungal agents, (iii) the population of patients at risk for serious Candida infections is well-defined and very large, and includes post-operative patients, transplant patients, cancer patients and low birth weight infants; and (iv) a high percentage of the patients who develop serious Candida infections are not neutropenic, and thus may respond to a vaccine. For these reasons, Candida is the most attractive fungal target for either passive or active immunotherapy.

Having determined the immunotherapeutic potential of members of the ALS family according to this invention, the gene, the protein gene product, conjugates, analogues, or derivative molecules thereof, and compositions containing specific monoclonal or polyclonal antisera may be used in treatment and/or prevention of candidal infections. Standard immunological techniques may be employed with the adhesion protein molecule, and its analogues, conjugates, or derivatives, to use the molecule as an immunogen in a pharmaceutically acceptable composition administered as a vaccine. For the purposes of this invention, “pharmaceutical” or “pharmaceutically acceptable” compositions are formulated by known techniques to be non-toxic and, when desired, used with carriers or additives that are approved for administration to humans in, for example, intravenous, intramuscular, intraperitoneal or sub-cutaneous injection. Such compositions may include buffers, salts or other solvents known to these skilled in the art to preserve the activity of the vaccine in solution.

With respect to the molecule used as the immunogen pursuant to the present invention, those of skill in the art will recognize that each protein molecule within the ALS family may be truncated or fragmented without losing the essential qualities as a vaccine. For example, the Als1p may be truncated to yield an N-terminal fragment by truncation from the C-terminal end with preservation of the functional properties described above and may include all or a portion of the GP1 anchor sequences on the central region. Likewise, C-terminal fragments may be created by truncation from the N-terminal end with preservation of the functional properties described above. Other modifications in accord with the foregoing rationale may be made pursuant to this invention to create other ALS protein analogs or derivatives, to achieve the benefits described herein with the native protein.

The goal of the immunotherapy provided by this invention is to interfere with regulation of filamentation, to block adherence of the organism to host constituents, and to enhance clearance of the organism by immunoeffector cells. Since endothelial cells cover the majority of the vasculature, specially selected strategies, compositions, and formulations to block the adherence of the organism to endothelial cells using antibodies are a preferred embodiment of the present invention and such adherence blocking strategies include active or passive immunotherapy directed against the candidal adhesin(s) disclosed herein. Specific anti-sera having demonstrated abilities to interrupt virulence factors and pathways implicated in virulence are identified herein based on the identification of the unique properties of the ALS family of proteins and specific derivatives thereof, including N-terminal fragments of the ALS proteins, specific monoclonal and polyclonal antisera against regions of the protein molecule, and polynucleotides selectively encoding this region.

Depending on the specific virulence of a strain in a clinical setting, a pharmaceutical composition comprising either monoclonal or polyclonal antibodies may be administered in a passive immunization therapy. Polyclonal antibodies are thought to involve fewer specific cross reactivity reactions that may lead to acute toxicity, whereas monoclonal antibodies provide more reproducible binding to a specific epitope of a target protein. Therefore, selection of the species for passive immunotherapy depends on the specific organism encoding the protein-antigen, as well as the specific antibody raised against the ALS protein. In either case, the antisera is specific to a portion of the ALS protein and functions to interrupt virulence regulatory pathways necessary for pathogenesis of the organism. Specifically, the antisera affects the Efg1p filamentation pathway and expression of the surface protein implicated in both floculation and adherence to endothelial cells. Characteristic antisera of the invention interrupt the role of ALS in filamentation and virulence mechanisms in both in vitro systems as well as animal models of disseminated candidiasis.

The method of the invention also includes ameliorating and/or preventing candidal infection by blocking the adherence of C. albicans to the endothelial cells of a host constituent. Thus, according to one aspect of the invention, a pharmaceutical composition comprising an ALS adhesin protein derivative, analogue, or conjugate is formulated as a vaccine in a pharmaceutical composition containing a biocompatible carrier for injection or infusion and is administered to a patient. Prior to injection, the adhesin protein may be formulated as a vaccine in a suitable vehicle, preferably a known immunostimulant such as a polysaccharide. Thus, according to a further aspect of the invention we provide a pharmaceutical composition comprising a candidal adhesin protein together with one or more pharmaceutically acceptable excipients in a formulation for use as a vaccine. Also, direct administration of antiserum raised against an ALS protein may be used as a therapeutic or prophylactic strategy to block the adherence of C. albicans to a mammalian host constituent. Thus, for example, any suitable host may be injected with protein and the serum collected to yield the desired anti-adhesin antibody after appropriate purification and/or concentration. Monoclonal antiserum against adhesin protein can be obtained by known techniques, Kohler and Milstein, Nature 256: 495-499 (1975), and may be humanized to reduce antigenicity, see U.S. Pat. No. 5,693,762, or produced by immunization of transgenic mice having an unrearranged human immunoglobulin gene, see U.S. Pat. No. 5,877,397, to yield high affinity (e.g. 10⁸, 10⁹, or 10¹⁹) anti-ALS IgG monoclonal antibodies.

A still further use of the invention, for example, is using an ALS adhesin protein to develop a specific clinical vaccine strategies for the prevention and/or amelioration of candidal infections. Thus, according to one aspect of the invention, for example, standard immunology techniques may be employed to construct a multi-protein or protein fragment component vaccine strategy that may enhance and/or elicit immune response from a host constituent to bock adherence of C. albicans. Also, known immunostimulatory compositions may be added to the vaccine formulation, wherein such compounds include known proteins, saccharides or oligonucleotides. (See Krieg U.S. Pat. No. 6,008,200).

A still further use of the invention, for example, is an isolated polynucleotide, RNA or DNA vaccine strategy wherein the ALS polynucleotide encoding an ALS protein or a fragment or variant thereof is administered according to a protocol designed to yield an immune response to the gene product. See e.g., Felgner U.S. Pat. No. 5,703,055. Generally, the naked polynucleotide is combined in a pharmaceutically acceptable injectable carrier and injected into muscle tissue where the polynucleotide is transported into cells and expressed to produce a selectively induced immunogenic response comprised of antibodies against the polypeptide encoded by the polynucleotide. The tissue into which the polynucleotide is introduced is preferably muscle, but can be any tissue that expresses the polynucleotide. The polynucleotide may be either a DNA or an RNA sequence and when the DNA is used, the DNA sequence can be inserted into a plasmid that also contains a replicator. In this embodiment, a method of immunization is provided by obtaining an expressible polynucleotide coding for an immunogenic ALS polypeptide, and introducing the polynucleotide into a patient to elicit expression of the ALS polypeptide and the generation of an immune response against the immunogen such that an anti-ALS antibody composition produced in vivo provides protection against Candidiasis by disrupting the virulence pathway, for example, as has been associated with ALS1p and the effector pathway for adhesion and filamentation of the Candida organism. Particularly preferred polynucleotide compositions encode N-terminal regions of an ALS polypeptide and code for the specific regions that elicit the antisera production in vivo that are shown herein to exhibit the prophylactic therapeutic utility derived from interruption of Candida virulence mechanisms.

A still further use of the invention, for example, is developing combination vaccine strategies. Thus, according to one aspect of the invention, for example, anti-ALS antibodies may be used with antibodies in treating and/or preventing candidal infections. See U.S. Pat. No. 5,578,309.

DESCRIPTION OF THE FIGURES

FIGS. 1A, 1B show the mediation of Als1p adherence of C. albicans to human umbilical vein endothelial cells. Values represent the mean±SD of at least three independent experiments, each performed in triplicate. (A) Endothelial cell adherence of ALS1/als2, als1/als1 and ALS1-complemented mutants and wild-type CAI12 (30) (B) Endothelial cell adherence of P_(ADH1)-ALS1 mutant that overexpresses ALS1, compared to wild type C. albicans. Statistical treatment was obtained by Wilcoxon rank sum test and corrected for multiple comparisons with the Bonferroni correction. *P<0.001 for all comparisons.

FIG. 2A-D shows the cell surface localization of Als1p on filaments of C. albicans by indirect immunofluorescence. Filamentation of C. albicans was induced by incubating yeast cells in RPMI 1640 medium with glutamine for 1.5 hours at 37° C. Als1p was detected by incubating organisms first with anti-Als1p mouse mAb followed by FITC-labeled goat anti-mouse IgG. C. albicans cell surface was also stained with anti-C. albicans polyclonal Ab conjugated with Alexa 594 (Molecular Probes, Eugene, Oreg.). Areas with yellow staining represent Als1p localization. (A) C. albicans wild-type. (B) als1/als1 mutant strain. (C) als1/als1 complemented with wild type ALS1 (D) P_(ADH1)-ALS1 overexpression mutant.

FIGS. 3A, 3B show the mediation of Als1p on C. albicans filamentation on solid medium. C. albicans blastospores were spotted on Lee's agar plates and incubated at 37° C. for 4 days (A) or 3 days (B).

FIGS. 4A, 4B show the control of ALS1 expression and the mediation of C. albicans filamentation by the EFG1 filamentation regulatory pathway. (A) Northern blot analysis showing expression of ALS1 in (i) mutants deficient in different filamentation regulatory pathways. (ii) efg1/efg1 mutant complemented with either EFG1 or P_(ADH1)-ALS1. Total RNA was extracted from cells grown in RPM1 1640+ glutamine medium at 37° C. for 90 minutes to induce filamentation. Blots were probed with ALS1 and TEF1. (B) Photomicrographs of the efg1/efg1 mutant and efg1/efg1 mutant complemented with P_(ADH1)-ALS1 grown on Lee's agar plates at 37° C. for 4 days.

FIGS. 5A, 5B show the reduction of virulence in the mouse model of hematogenously disseminated candidiasis by (A) Male Balb/C mice (n=30 for each yeast strain) were injected with stationary phase blastospores (10⁶ per mouse in 0.5 ml of PBS). Curves are the compiled results of three replicate experiments (n=30 mice for each strain). The doubling times of all strains, grown in YPD at 30° C., ranged between 1.29 to 1.52 hours and were not statistically different from each other. Southern blot analysis of total chromosomal DNA was used to match the identity of the genotype of C. albicans strains retrieved from infected organs with those of C. albicans strains used to infect the mice. Statistical analysis was obtained by Wilcoxon rank sum test and corrected for multiple comparisons with the Bonferroni correction. *P<0.002 for the als1/als1 mutant versus each of the other strains. (B) Histological micrographs of kidneys infected with C. albicans wild-type, homozygous als1 null mutant, or heterozygous ALS1 complemented mutant. Kidney samples were retrieved 28 hours (a) or 40 (b) hours post infection, fixed in paraformaldehyde and sections were stained with silver (magnification, X400). Arrows denote C. albicans cells.

FIG. 6 shows the prophylactic effect of anti-ALS antibody against disseminated candidiasis as a function of surviving animals over a 30-day period for animals infused with anti-Als1p polyserum.

FIG. 7 is the protein sequence alignment of the N-terminal portion of select ALS proteins arranged by adherence phenotype. The top three lines are the sequences from ALS proteins that bind endothelial cells: ALS1 (SEQ ID NO: 25), ALS3 (SEQ ID NO: 26), and ALS 5 (SEQ ID NO: 27), and the bottom three sequences from ALS proteins that do not bind endothelial cells: ALS6 (SEQ ID NO: 28), ALS 7 (SEQ ID NO: 29), and ALS 9 (SEQ ID NO: 30). The line labeled “Consensus” includes the following amino acid sequences “gdtf” (SEQ ID NO: 31); “mpcv” (SEQ ID NO: 32); “yatc” (SEQ ID NO: 33); “fnvgg” (SEQ ID NO: 34); “dskcf” (SEQ ID NO: 35); “ntvtf” (SEQ ID NO: 36); “idcs” (SEQ ID NO: 37); “pagyrpf” (SEQ ID NO: 38); “ttlpf” (SEQ ID NO: 39); “pipttt” (SEQ ID NO: 40); “tatv” (SEQ ID NO: 41); “tvttt” (SEQ ID NO: 42); and “nptvttt” (SEQ ID NO: 43).

DETAILED DESCRIPTION OF THE INVENTION

The nature of the pathogenesis of C. albicans by adherence to endothelial cells is discussed in U.S. Pat. No. 5,578,309 which is specifically incorporated herein by reference in its entirety. For a description of the ALS1 gene and characteristics thereof, including the characterization of the gene product as an adhesin, see Fu, Y., S. G. Filler, B. J. Spellberg, W. Fonzi, A. S. Ibrahim, T. Kanbe, M. A. Ghannoum, and J. E. J. Edwards. 1998. Cloning and characterization of CAD I/AAF1, a gene from Candida albicans that induces adherence to endothelial cells after expression in Saccharonzyces cerevisiae. Infect. Immun. 66:2078-2084; Fu, Y., G. Rieg, W. A. Forizi, P. H. Belanger, J. E. J. Edwards, and S. G. Filler. 1998. Expression of the Candida albicans gene ALS1 in Saccharomyces cerevisiae induces adherence to endothelial and epithelial cells. Infect. Immun. 66:1783-1786; Hoyer, L. L. 1997. The ALS gene family of Candida albicans. International Society for Human and Animal Mycology Salsimorge, Italy: (Abstract); Hoyer, L. L., S. Scherer, A. R. Shatzman, and G. P. Livi. 1995. Candida albicans ALS1: domains related to a Saccharonzyces cerevisiae sexual agglutinin separated by a repeating motif. Mol. Microbiol. 15:39-54. The polynucleotide sequence of the ALS1 gene and protein are SEQ ID NO:7 and NO:8, respectively. The remaining numbers of the ALS family of gene and protein ALS-2-ALS-9, are SEQ ID NO:9-SEQ ID. NO:24. Note that the form sometimes known as ALS-N is ALS-9 and ALA-1 is ALS-5.

The following Examples illustrate the immunotherapeutic utility of the class of ALS protein molecules as the basis for prevention or treatment of disseminated candidiasis. Example 1 describes the preparation of an ALS1 null mutant and a strain of C. albicans characterized by over-expression of ALS1 to confirm the mediation of adherence to endothelial cells. Example 2 describes the localization of Als1p and the implication of the efg filamentation regulatory pathway. Example 3 describes the purification of ALS1 adhesin protein. Example 4 describes the preparation of antibodies raised against the ALS1 surface adhesin protein to be used to demonstrate the blocking of the surface adhesin protein. Example 5, describes the blocking of adherence in vivo, using both polyclonal and monoclonal antibodies raised against the ALS1 surface adhesion protein as described herein to protect against disseminated candidiasis in a mouse model. Example 6 describes a polynucleotide vaccination strategy to cause in vivo expression of an antigenic ALS1p polypeptide to create a protective immune response.

Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, preferred methods and materials are described. As used herein, the following terms have the meanings ascribed to them unless specified otherwise.

“Polynucleotide” refers to a polymer composed of nucleotide units (ribonucleotides, deoxyribonucleotides, related naturally occurring structural variants, and synthetic non-naturally occurring analogs thereof) linked via phosphodiester bonds, related naturally occurring structural variants, and synthetic non-naturally occurring analogs thereof. Thus, the term includes nucleotide polymers in which the nucleotides and the linkages between them include non-naturally occurring synthetic analogs, such as, for example and without limitation, phosphorothioates, phosphoramidates, methyl phosphonates, chiral-methyl phosphonates, 2-O-methyl ribonucleotides, peptide-nucleic acids (PNAs), and the like. Such polynucleotides can be synthesized, for example, using an automated DNA synthesizer. The term “gene” typically refers to a large number of polynucleotides that form a single functional unit that is translated and transcribed to express a polypeptide of sufficient length to be immunogenic.

“Polypeptide” refers to a polymer composed of amino acid residues, related naturally occurring structural variants, and synthetic non-naturally occurring analogs thereof linked via peptide bonds, related naturally occurring structural variants, and synthetic non-naturally occurring analogs thereof. Synthetic polypeptides can be synthesized, for example, using an automated polypeptide synthesizer.

“Conservative substitution” refers to the substitution in a polypeptide of an amino acid with a functionally similar amino acid. The following six groups each contain amino acids that are conservative substitutions for one another:

1) Alanine (A), Serine (S), Threonine (T);

2) Aspartic acid (D), Glutamic acid (E);

3) Asparagine (N), Glutamine (Q);

4) Arginine (R), Lysine (K);

5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); and

6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W).

“Antibody” or “antisera” refers to a polypeptide substantially encoded by an immunoglobulin gene or immunoglobulin genes, or fragments thereof, which specifically bind and recognize an immunogen. The recognized immunoglobulin genes include the kappa, lambda, alpha, gamma, delta, epsilon and mu constant region genes, as well as the myriad immunoglobulin variable region genes. Antibodies exist, e.g., as intact immunoglobulins or as a number of well characterized fragments produced by digestion with various peptidases. This includes, e.g., Fab′ and F(ab)′.sub.2 fragments. The term “antibody,” as used herein, also includes antibody fragments either produced by the modification of whole antibodies or those synthesized de novo using recombinant DNA methodologies.

An antibody “is specific” or “specifically binds” to a protein when the antibody functions in a binding reaction which is determinative of the presence of the protein in the presence of a heterogeneous population of proteins and other biologics. Thus, under designated immunoassay conditions, the specified antibodies bind preferentially to a particular protein and do not bind in a significant amount to other proteins present in the sample. Specific binding to a protein under such conditions requires an antibody that is selected for its specificity for a particular protein. A variety of immunoassay formats may be used to select antibodies specifically immunoreactive with a particular protein. For example, solid-phase ELISA immunoassays are routinely used to select monoclonal antibodies specifically immunoreactive with a protein. See Harlow and Lane (1988) Antibodies, A Laboratory Manual, Cold Spring Harbor Publications, New York, for a description of immunoassay formats and conditions that can be used to determine specific immunoreactivity.

“Substantially pure” means an object species is the predominant species present (i.e., on a molar basis, more abundant than any other individual macromolecular species in the composition), and a substantially purified fraction is a composition wherein the object species comprises at least about 50% (on a molar basis) of all macromolecular species present. Generally, a substantially pure composition means that about 80% to 90% or more of the macromolecular species present in the composition is the purified species of interest. The object species is purified to essential homogeneity (contaminant species cannot be detected in the composition by conventional detection methods) if the composition consists essentially of a single macromolecular species. Solvent species, small molecules (<500 Daltons), stabilizers (e.g., BSA), and elemental ion species are not considered macromolecular species for purposes of this definition.

“Pharmaceutical composition” refers to a composition suitable for pharmaceutical use in a mammal. A pharmaceutical composition comprises a pharmacologically effective amount of an active agent and a pharmaceutically acceptable carrier. “Pharmacologically effective” or phamaceutically effective” amount refers to that amount of an agent effective to produce the intended pharmacological result. “Pharmaceutically acceptable carrier” refers to any of the standard pharmaceutical carriers, buffers, and excipients, such as a phosphate buffered saline solution, 5% aqueous solution of dextrose, and emulsions, such as an oil/water or water/oil emulsion, and various types of wetting agents and/or adjuvants. Suitable pharmaceutical carriers and formulations are described in Remington's Pharmaceutical Sciences, 19th Ed. (Mack Publishing Co., Easton, 1995). Preferred pharmaceutical carriers depend upon the intended mode of administration of the active agent. Typical modes of administration include enteral (e.g., oral) or parenteral (e.g., subcutaneous, intramuscular, or intravenous intraperitoneal injection; or topical, transdermal, or transmucosal administration).

A “prophylactic” treatment is a treatment administered to a subject who does not exhibit overt symptoms or signs of a disease or exhibits only early signs for the purpose of decreasing the risk of developing pathology.

A “therapeutic” treatment is a treatment administered to a subject who exhibits signs of pathology for the purpose of diminishing or eliminating those signs.

Example 1 Als1 Mediates Adherence of C. albicans to Endothelial Cells

The URA blaster technique was used to construct a null mutant of C. albicans that lacks expression of the Als1p. The als1/als1 mutant was constructed in C. albicans strain CAI4 using a modification of the Ura-blaster methodology [W. A. Fonzi and M. Y. Irwin, Genetics 134, 717 (1993)] as follows: Two separate als1-hisG-IRA3-hisG-als1 constructs were utilized to disrupt the two different alleles of the gene. A 4.9 kb ALS1 coding sequence was generated with high fidelity PCR (Boehringer Mannheim, Indianapolis, Ind.) using the primers: 5′-CCGCTCGAGATGCTTCAACAATTTACATTGTTA-3′ (SEQ ID NO. 1) and 5′-CCGCTCGAGTCACTAAATGAACAAGGACAATA3′ (SEQ ID NO. 2). Next, the PCR fragment was cloned into pGEM-T vector (Promega, Madison, Wis.), thus obtaining pGEM-T-ALS1. The hisG-URA3-hisG construct was released from pMG-7 by digestion with KpnI and Hind3 and used to replace the portion of ALS1 released by Kpn1 and Hind3 digestion of pGEM-T-ALS1. The final als1-hisG-URA3-hisG-als1 construct was released from the plasmid by digestion with Xhol and used to disrupt the first allele of ALS1 by transformation of strain CAI-4.

A second als1-hisG-URA3-hisG-als1 construct was generated in two steps. First, a Bgl2-Hind3 hisG-URA3-hisG fragment of pMB7 was cloned into the Bam1H-Hind3 sites of pUC19, thereby generating pYC2. PYC2 was then digested with Hind3, partially filled in with dATP and dGTP using T4 DNA polymerase, and then digested with Sma1 to produce a new hisG-URA3-hisG fragment. Second, to generate ALS1 complementary flanking regions, pGEM-T-ALS1 was digested with Xbal and then partially filled in with dCTP and dTTP. This fragment was digested with HpaI to delete the central portion of ALS1 and then ligated to the hisG-URA3-hisG fragment generating pYC3. This plasmid was then digested by Xhol to release a construct that was used to disrupt the second allele of the ALS1. Growth curves were done throughout the experiment to ensure that the generated mutations had no effect on growth rates. All integrations were confirmed by Southern blot analysis using a 0.9 kb ALS1 specific probe generated by digestion of pYF5 with XbaI and HindIII.

The null mutant was compared to C. albicans CAI-12 (a URA+revertant strain) for its ability to adhere in vitro to human umbilical vein endothelial cells. For adherence studies, yeast cells from YPD (2% glucose, 2% peptone, and 1% yeast extract) overnight culture, were grown in RPMI with glutamine at 25° C. for 1 hour to induce Als1p expression. 3×10² organisms in Hanks balanced salt solution (HBSS) (Irvine Scientific, Irvine, Calif.) were added to each well of endothelial cells, after which the plate was incubated at 37° C. for 30 minutes. The inoculum size was confirmed by quantitative culturing in YPD agar. At the end of incubation period, the nonadherent organisms were aspirated and the endothelial cell monolayers were rinsed twice with HBSS in a standardized manner. The wells were over laid with YPD agar and the number of adherent organisms were determined by colony counting. Statistical treatment was obtained by Wilcoxon rank sum test and corrected for multiple comparisons with the Bonferroni correction. P<0.001.

Referring to FIG. 1, a comparison of the ALS1/ALS1 and als1/als1 strain showed that the ALS1 null mutant was 35% less adherent to endothelial cells than C. albicans CAI-12. To reduce background adherence, the adherence of the wild-type strain grown under non-ALS1 expressing conditions was compared with a mutant autonomously expressing Als1p. This mutant was constructed by integrating a third copy of ALS1 under the control of the constitutive ADH1 promoter into the wild-type C. albicans. To achieve constitutive expression of the ALS1 in C. albicans, a blunt-ended PCR generated URA3 gene is ligated into a blunt-edged Bgl2 site of pOCUS-2 vector (Novagen, Madison, Wis.), yielding pOU-2. A 2.4 kb Not1-Stul fragment, which contained C. albicans alcohol dehydrogenase gene (ADH1) promoter and terminator (isolated from pLH-ADHpt, and kindly provided by A. Brown, Aberdeen, UK), was cloned into pOU-2 after digestion with Not1 and Stul. The new plasmid, named pOAU-3 had only one Bgl2 site between the ADH1 promoter and terminator. ALS1 coding sequence flanked by BamH1 restriction enzyme sites was generated by high fidelity PCR using pYF-5 as a template and the following primers: 5′-CGGGATCCAGATGCTTCA-ACAATTTACATTG-3′ (SEQ ID NO.3) and 5′-CGGGATCCTCACTAAATGAACAAGGACAATA-3′ (SEQ ID NO.4). This PCR fragment was digested with BamH1 and then cloned into the compatible Bgl2 site of pOAU-3 to generate pAU-1. Finally, pAU-1 was linearized by Xbal prior to transforming C. albicans CAI-4. The site-directed integration was confirmed by Southern Blot analysis.

Referring to FIG. 1B, overexpressing ALS1 in this P_(ADH1)-ALS1 strain resulted in a 76% increase in adherence to endothelial cells, compared to the wild-type C. albicans. In comparing endothelial cell adherence of the wild-type to that of the overexpressing mutant, yeast cells were grown overnight in YPD at 25° C. (non-inducing condition of Als1p). Als1p expression was not induced to reduce the background adherence of the wild-type, thus magnifying the role of Als1p in adherence through P_(ADH1)-ALS1 hybrid gene. The adherence assay was carried out as described above. Statistical treatment was obtained by Wilcoxon rank sum test and corrected for multiple comparisons with the Bonferroni correction. P<0.001.

A monoclonal anti-Als1p murine IgG antibody was raised against a purified and truncated N-terminus of Als1p (amino acid #17 to #432) expressed using Clontech YEXpress™ Yeast Expression System (Palo Alto, Calif.). The adherence blocking capability of these monoclonal anti-Als1p antibodies was assessed by incubating C. albicans. cells with either anti-Als1 antibodies or mouse IgG (Sigma, St. Louis, Mo.) at a 1:50 dilution. After which the yeast cells were used in the adherence assay as described above. Statistical treatment was obtained by Wilcoxon rank sum test and corrected for multiple comparisons with the Bonferroni correction. P<0.001. The results revealed that the adherence of the P_(ADH1)-ALS1 strain was reduced from 26.8%±3.5% to 14.7%±5.3%. Thus, the effects of ALS1 deletion and overexpression demonstrate that Als1p mediates adherence of C. albicans to endothelial cells.

Example 2 Localization of Als1p

For a number of the ALS family to function as an adhesin protein, it must be located on the cell surface. The cell surface localization of Als1p, for example, was verified using indirect immunofluorescence with the anti-Als1p monoclonal antibody. Diffuse staining was detected on the surface of blastospores during exponential growth. This staining was undetectable on blastospores in the stationary phase. Referring to FIG. 2A, when blastospores were induced to produce filaments, intense staining was observed that localized exclusively to the base of the emerging filament. No immunofluorescence was observed with the als1/als1 mutant, confirming the specificity of this antibody for Als1p. See FIG. 2B. These results establish that Als1p is a cell surface protein.

The specific localization of Als1p to the blastospore-filament junction implicates Als1p in the filamentation process. To determine the mechanism, the filamentation phenotype of the C. albicans ALS1 mutants was analyzed. Referring to FIG. 3A, the als1/als1 mutant failed to form filaments after a 4 day incubation on Lee's solid medium, while both the ALS1/ALS1 and ALS1/als1 strains as well as the ALS1-complemented mutant produced abundant filaments at this time point. The als1/als1 mutant was capable of forming filaments after longer periods of incubation. Furthermore, overexpressing ALS1 augmented filamentation: the P_(ADH1)-ALS1 strain formed profuse filaments after a 3 day incubation, whereas the wild-type strain produced scant filaments at this time point. See FIG. 3B. To further confirm the role of Als1p in filamentation, a negative control was provided using mutant similar to the ALS1 overexpression mutant, except the coding sequence of the ALS1 was inserted in the opposite orientation. The filamentation phenotype of the resulting strain was shown to be similar to that of the wild-type strain. The filament-inducing properties of Als1p are specific to cells grown on solid media, because all of the strains described above filamented comparably in liquid media. The data demonstrates that Als1p promotes filamentation and implicates ALS1 expression in the regulation of filamentation control pathways. Northern blot analysis of ALS1 expression in mutants with defects in each of these pathways, including efg1/efg1, cph1/cph1, efg1/efg cph1/cph1, tup1/tup1, and cla4/cla4 mutants were performed. Referring to FIG. 4A, mutants in which both alleles of EFG1 had been disrupted failed to express ALS1. Introduction of a copy of wild-type EFG1 into the efg1/efg1 mutant restored ALS1 expression, though at a reduced level. See FIG. 4B. Also, as seen in FIG. 4A, none of the other filamentation regulatory mutations significantly altered ALS1 expression (FIG. 4A). Thus, Efg1p is required for ALS1 expression.

If Efg1p stimulates the expression of ALS1, which in turn induces filamentation, the expression of ALS1 in the efg1/efg1 strain should restore filamentation. A functional allele of ALS1 under the control of the ADH1 promoter was integrated into the efg1/efg1 strain. To investigate the possibility that ALS1 gene product might complement the filamentation defect in efg1 null mutant, an Ura efg1 null mutant was transformed with linearized pAU-1. Ura⁺ clones were selected and integration of the third copy of ALS1 was confirmed with PCR using the primers: 5′-CCGTTTATACCATCCAAATC-3′(SEQ ID NO. 5) and 5′-CTACATCCTCCAATGATATAAC-3′ (SEQ ID NO. 6). The resulting strain expressed ALS1 autonomously and regained the ability to filament on Lee's agar. See FIGS. 4B and C. Therefore, Efg1p induces filamentation through activation of ALS1 expression.

Because filamentation is a critical virulence factor in C. albicans, delineation of a pathway that regulates filamentation has important implications for pathogenicity. Prior to ALS1, no gene encoding a downstream effector of these regulatory pathways had been identified. Disruption of two other genes encoding cell surface proteins, HWP1 AND INTI, results in mutants with filamentation defects. Although HWP1 expression is also regulated by Efg1p, the autonomous expression of HWP1 in the efg1/efg1 mutant fails to restore filamentation. Therefore Hwp1p alone does not function as an effector of filamentation downstream of EFG1. Also, the regulatory elements controlling INT1 expression are not known. Thus, Als1p is the first cell-surface protein identified that functions as a downstream effector of filamentation, thereby suggesting a pivotal role for this protein in the virulence of C. albicans.

The contribution of Als1p to C. albicans virulence was tested in a model of hematogenously disseminated candidiasis, A. S. Ibrahim et al., Infect. Immun. 63, 1993 (1995). Referring to FIG. 5A, mice infected with the als1/als1 null mutant survived significantly longer than mice infected with the ALS1/ALS1 strain, the ALS1/als1 mutant or the ALS1-complemented mutant. After 28 hours of infection, the kidneys of mice infected with the als1/als1 mutant contained significantly fewer organisms (5.70±0.46 log₁₀ CFU/g) (P<0.0006 for both comparisons). No difference was detected in colony counts of organisms recovered from spleen, lungs, or liver of mice infected with either of the strains at any of the tested time points. These results indicate that immunotherapeutic strategies using ALS proteins as a vaccine have a protective prophylactic effect against disseminated candidiasis. See SEQ ID NOS. 10, 12, 14, 16, 18, 20, 22, and 24. Referring to FIG. 5B, examination of the kidneys of mice after 28 hours of infection revealed that the als1/als1 mutant produced significantly shorter filaments and elicited a weaker inflammatory response than did either the wild-type of ALS1-complemented strains. However, by 40 hours of infection, the length of the filaments and the number of leukocytes surrounding them were similar for all three strains.

The filamentation defect of the als1/als1 mutant seen on histopathology paralleled the in vitro filamentation assays on solid media. This mutant showed defective filamentation at early time points both in vivo and in vitro. This defect eventually resolved with prolonged infection/incubation. These results suggest that a filamentation regulatory pathway that is independent of ALS1 may become operative at later time points. The activation of this alternative filamentation pathway by 40 hours of infection is likely the reason why mice infected with the als1/als1 mutant subsequently succumbed in the ensuing 2-3 days.

Collectively, these data demonstrate that C. albicans ALS1 encodes a cell surface protein that mediates both adherence to endothelial cells and filamentation. Als1p is the only identified downstream effector of any known filamentation regulatory pathway in C. albicans. Additionally, Als1p contributes to virulence in hematogenous candidal infection. The cell surface location and dual functionality of Als1p make it an attractive target for both drug and immune-based therapies.

Example 3 Purification of ALS1 Adhesin Protein, Truncated N-Terminal Protein

For use as an immunogen, an ALS protein synthesized by E. coli is adequate when vaccination with a traditional protocol yield an immune response generating B cells expressing measurable anti-ALS anti-sera or levels of serum Ig from which polyclonals may be obtained. However, eukaryotic proteins synthesized by E. coli may not be functional due to improper folding or lack of glycosylation. Therefore, to determine if the ALS1 protein can block the adherence of C. albicans to endothelial cells, the protein is, preferably, purified from genetically engineered C. albicans, and formulated into a substantially pure pharmaceutical composition that is pharmacologically effective for prophylactic or therapeutic treatment of disseminated candidiasis.

PCR was used to amplify a fragment of ALS1, from nucleotides 52 to 1296. This 1246 bp fragment encompassed the N-terminus of the predicted ALS1 protein from the end of the signal peptide to the beginning of the tandem repeats. This region of ALS1 was amplified because it likely encodes the binding site of the adhesin, based on its homology to the binding region of the S. cerevisiae Agα1 gene product. In addition, this portion of the predicted ALS1 protein has few glycosylation sites and its size is appropriate for efficient expression in E. coli.

The N-terminal fragment of ALS1 was ligated into pQE32 to produce pINS5. In this plasmid, the N-terminal segment of the protein is expressed under control of the lac promoter and it has a 6-hits tag fused to its N-terminus so that it can be affinity purified. We transformed E. coli with pINS5, grew it under inducing conditions (in the presence of IPTG), and then lysed the cells. The cell lysate was passed through a Ni²⁺-agarose column to affinity purify the ALS1-6H is fusion protein. This procedure yielded substantial amounts of ALS1-6H is. The fusion protein was further purified by SDS-PAGE. The band containing the protein was excised from the gel so that antiserum can be raised against it as described in detail herein. It will be appreciated by one skilled in the art that the surface adhesin protein according to the invention may be prepared and purified by a variety of known processes without departing from the spirit of the present invention based on the polynucleotide and polypeptide sequences of listed in SEQ ID. NO.1-SEQ ID NO.18. As noted above, analogues and derivatives of ALS1p may be prepared by known techniques based on conserved principles of amino acid substitution and nucleotide encoding degeneracy without departing from the invention. Thus, Such compositions may exhibit at least one conservative substitution in the polypeptide sequence and exhibit the same effect in disruption of adherence and filamentation pathways as the native ALS1p and antibodies that specifically bind thereto as described herein.

Example 4 Raising Polyclonal Antisera against ALS1 Protein

To determine whether antibodies against the ALS1 protein block the adherence of Candida albicans to endothelial and epithelial cells, and the selected host constituent in vitro, rabbits were inoculated with S. cerevisiae transformed with ALS1 protein. The immunization protocol used was the dose and schedule used by Hasenclever and Mitchell for production of antisera that identified the antigenic relationship among various species of Candida. Hasenclever, H. F. and W. O. Mitchell. 1960. Antigenic relationships of Torulopsis glabrata and seven species of the genus Candida. J. Bacteriol. 79:677-681. Control antisera were also raised against S. cerevisiae transformed with the empty plasmid. All yeast cells were grown in galactose to induce expression of the ALS genes. Before being tested in the adherence experiments, the serum was heat-inactivated at 56 C to remove all complement activity.

Sera from immunized rabbits were absorbed with whole cells of S. cerevisiae transformed with empty plasmid to remove antibodies that are reactive with components of the yeast other than ALS1 protein. The titer of the antisera was determined by immunofluorescence using S. cerevisiae that express the ALS1 gene. FITC-labeled anti-rabbit antibodies were purchased from commercial sources (Southern Biotechnology, Inc). Affinity-purified secondary antibodies were essential because many commercially available sera contain antibodies reactive with yeast glucan and mannan. The secondary antibodies were pretested using Candida albicans as well as S. cerevisiae transformed with the plasmid and were absorbed as needed to remove any anti-S. cerevisiae or anti-Candida antibodies. Negative controls were 1) preimmune serum, 2) S. cerevisiae transformed with the empty plasmid, and 3) S. cerevisiae transformed with the ALS gene but grown under conditions that suppress expression of the ALS gene (glucose).

In addition to the above experiments, Western blotting was used to provide further confirmation that an antiserum binds specifically to the ALS1 protein against which it was raised. S. cerevisiae transformed with the ALS1 were grown under inducing conditions and their plasma membranes were isolated by standard methods. Panaretou, B. and P. Piper. 1996. Isolation of yeast plasma membranes. p. 117-121. In LH. Evans. (ed.), Yeast Protocols. Methods in Cell and Molecular Biology. Humana Press, Totowa, N.J. Plasma membranes were also prepared from S. cerevisiae transformed with the empty plasmid and grown under identical conditions. The membrane proteins were separated by SDS-PAGE and then transferred to PVDF membrane by electroblotting. Harlow, E. and D. Lane. 1988. Antibodies: A Laboratory Manual. Cold Spring Harbor Laboratory Press. After being blocked with nonfat milk, the blot was incubated with the ALS antiserum. The preabsorbed antiserum did not react with proteins extracted from S. cerevisiae containing empty plasmid. This antiserum blocked the adherence of S. cerevisiae pYF5 (a clone that expresses Candida albicans ALS1) to endothelial cells.

Example 5 Antibodies Against Specific ALS Proteins Prophylactically Protect Mice from Mucosal and Hematogenously Disseminated Candidal Infections

Antisera that block the adherence of a clone of S. cerevisiae transformed with an ALS1 were demonstrated to protect mice from intravenous challenge with Candida albicans. The antisera against the ALS proteins were first tested in the murine model of hematogenously disseminated candidiasis. Affinity-purified anti-ALS antibodies are effective in preventing adhesion of yeast cells to various substrates (see Example 3). Affinity-purification is useful in this system because antibody doses can be accurately determined. Moreover, the unfractionated antisera will undoubtedly contain large amounts of antibody directed toward antigens on the S. cerevisiae carrier cells. Many of these anti-Saccharomyces antibodies would likely bind to C. albicans and make interpretation of the results impossible. Additionally, it is quite possible that the procedure used to elute antibodies from S. cerevisiae that express the ALS protein may also elute small amounts of yeast mannan or glucan that could have adjuvant-like activity. The immunoaffinity-purified antibodies are further purified before use. They may also be preabsorbed with mouse splenocytes.

Antibody doses may be administered to cover the range that brackets the levels of serum antibody that can be expected in most active immunization protocols and to cover the range of antibody doses that are typically used for passive immunization in murine models of candidiasis. See Dromer, F., J. Charreirc, A. Contrepois, C. Carbon, and P. Yeni. 1987, Protection, of mice against experimental cryptococcosis by anti-Cryptococcus neoformas monoclonal antibody, Infect. Inimun. 55:749-752; Han, Y. and J. E. Cutler. 1995, Antibody response that protects against disseminated candidiasis, Infect. Immun. 63:2714-2719; Mukherjee, J., M. D. Scharff, and A. Casadevall. 1992, Protective murine monoclonal antibodies to Cryptococcus neoformas, Infect. Immun. 60:4534-4541; Sanford, J. E., D. M. Lupan, A. M. Schlageter, and T. R. Kozel. 1990, Passive immunization against Cryptococcus neoformas with an isotype-switch family of monoclonal antibodies reactive with cryptococcal polysaccharide, Infect. Inunun. 58:1919-1923. BALB/c mice (female, 7 week old, the NCI) were given anti-ALS that had been absorbed with mouse splenic cells by an intraperitoneal (i.p.) injection. Control mice received prebled serum that had been absorbed with mouse spenic cells, intact anti-ALS serum, or DPBS, respectively. For the pre-absorption, 2 ml of anti-ALS or prebled sera were mixed with 100μl of mouse (BALB/c, 7 weeks old female, NCI) splenic cells (app. 9×10⁶ cells per ml) at room temperature for 20 minutes. The mixture was washed with warm sterile DPBS by centrifugation (@ 300×g) for 3 minutes. This procedure was repeated three times. The volume of i.p. injection was 0.4 ml per mouse. Four hours later, the mice were challenged with C. albicans (strain CA-1; 5×10⁵ hydrophilic yeast cells per mouse) by i.v. injection. Then, their survival times were measured. See FIG. 6.

Previous studies have shown that antibodies administered via the intraperitoneal route are rapidly (within minutes) and almost completely transferred to the serum (Kozel and Casadevall, unpublished observations). As a control for effects of administering the antibody preparations, a parallel group of mice were treated with antibodies isolated from pre-immune serum that has been absorbed with S. cerevisiae transformed with the ALS gene. The survival time and numbers of yeast per gram of kidney were measured. Again, referring to FIG. 6, mice infected intravenously with 10⁶ blastopores of ALS1 null mutant had a longer median survival time when compared to mice infected with Candida albicans CAI-12 or Candida albicans in which one allele of the ALS1 had been deleted (p=0.003).

The N-terminal portion of Als1p was used to generate a mouse monoclonal anti-Als1p antibody using modification of the method described by Brawner and Cutler (1984). Briefly, 6-week old female BALB/c mice (NCI) were immunized by subcutaneous injection with 125 μg of the purified N-terminus of the Als1p in 0.25 ml of complete Freund's adjuvant (Gibco BRL). After 21 days, the mice received a subcutaneous booster injection of another 125 μg of the purified N-terminus of the Als1p in 0.25 ml of incomplete Freund's adjuvant. On day 28, the mice sera were assessed for anti-Als1p antibodies using enzyme-linked immunosorbent assay (ELISA) plates coated with the N-terminus of the Als1p. A final booster injection of 15 μg of the Als1p N-terminus without adjuvant was administered intravenously to mice that tested positive for anti-Als1p antibodies 31 days after the initial immunization, and splenocytes were prepared for hybridoma production as described previously (Brawner and Cutler, 1984). Hybridoma antibody production was determined using ELISA plates coated with the purified N-terminus of the Als1p. One of the hybrids obtained produced antibody that agglutinated C. albicans and was cloned four times by limiting dilution. A hybridoma cell line expressing antibody that binds to the same epitope was developed. This antibody reacted to S. cerevisiae that overexpressed Als1p, but not to S. cerevisiae transformed with the empty plasmid. The antibody also did not react with S. cerevisiae overexpressing Als5p, Als6p and was only weakly reactive against Als1p. ALS3p in C. albicans based upon the failure of the MAb to recognize any protein in the als1 null mutant strain upon germination. Heavy- and light chain-specific anti-mouse immunoglobulins (ICN Biomedicals) were used in ELISA to isotype this monoclonal antibody. The monoclonal antibody was isotyped to IgG1 with a kappa light chain. Mice administered monoclonal antibodies against the N-terminal domain of ALS1p exhibit a prophylactic and therapeutic effect against disseminated candidiasis.

Example 6 Polynucleotide Vaccination Produces Antibodies In Vivo to Alleviate Disseminated Candidal Infections

In this embodiment, an immunogenic ALS polypeptide is introduced to a patient by delivering an effective amount of pharmaceutically acceptable polynucleotide coding for the selected immunogenic ALS polypeptide whereby the polynucleotide is expressed in vivo and the patient generates an immune response to the immunogen, thereby immunizing the patient in an equivalent manner to that demonstrated above for the protein. For example, immunogenic ALS1 polynucleotide compositions, suitable to be used as vaccines, may be prepared from the ALS genes and vectors as disclosed herein. The vaccine elicits an immune response in a subject which includes the production of anti-ALS antibodies that exhibit specificities for the selected ALS molecule, and may exhibit similar affinities and binding to similar epitopes as the polyclonal and monoclonal antibodies described herein. Immunogenic compositions, including vaccines, containing the ALS nucleic acid may be prepared as injectables, in physiologically-acceptable liquid solutions or emulsions for polynucleotide administration. The nucleic acid may be associated with liposomes, such as lecithin liposomes or other liposomes known in the art, as a nucleic acid liposome (for example, as described in WO 9324640) or the nucleic acid may be associated with an adjuvant. Liposomes comprising cationic lipids interact spontaneously and rapidly with polyanions, such as DNA and RNA, resulting in liposome/nucleic acid complexes that capture up to 100% of the polynucleotide. In addition, the polycationic complexes fuse with cell membranes, resulting in an intracellular delivery of polynucleotide that bypasses the degradative enzymes of the lysosomal compartment. Published PCT application WO 94/27435 describes compositions for genetic immunization comprising cationic lipids and polynucleotides. Agents which assist in the cellular uptake of nucleic acid, such as calcium ions, viral proteins and other transfection facilitating agents, may advantageously be used. Both liquid as well as lyophilized forms that are to be reconstituted will comprise agents, preferably buffers, in amounts necessary to suitably adjust the pH of the injected solution.

For any parenteral use, particularly if the formulation is to be administered intravenously, the total concentration of solutes should be controlled to make the preparation isotonic, hypotonic, or weakly hypertonic. Non-ionic materials, such as sugars, are preferred for adjusting tonicity, and sucrose is particularly preferred. Any of these forms may further comprise suitable formulatory agents, such as starch or sugar, glycerol or saline. The compositions per unit dosage, whether liquid or solid, may contain from 0.1% to 99% of polynucleotide material.

The DNA sequences used in these methods can be those sequences which do not integrate into the genome of the host cell. These may be non-replicating DNA sequences, or specific-replicating sequences genetically engineered to lack the genome-integration ability. The naked ALS polynucleotide materials comprise the DNA of SEQ ID NO.:7, 9, 11, 13, 15, 17, 19, 21, or 23 or in RNA sequences coding for the ALS1p polypeptide of SEQ ID NO.:8, 10, 12, 14, 16, 18, 20, 22, or 24 including conservative substitutions and corresponding polynucleotides encoding such analogues or derivatives. With the availability of automated nucleic acid synthesis equipment, both the DNA sequences and the corresponding RNA sequences can be synthesized directly or derived from the native organism.

Where the polynucleotide is to be DNA, promoters suitable for use in various vertebrate systems are well known. For example, for use in murine systems, suitable strong promoters include RSV LTR, MPSV LTR, SV40 IEP, and metallothionein promoter. In humans, on the other hand, promoters such as CMV IEP may advantageously be used. When the polynucleotide is mRNA, it can be readily prepared from the corresponding DNA in vitro. For example, conventional techniques utilize phage RNA polymerases SP6, T3, or T7 to prepare mRNA from DNA templates in the presence of the individual ribonucleoside triphosphates. An appropriate phage promoter, such as a T7 origin of replication site is placed in the template DNA immediately upstream of the gene to be transcribed. Systems utilizing T7 in this manner are well known, and are described in the literature, e.g., in Current Protocols in Molecular Biology, §3.8 (vol. 1 1988).

To produce the composition for injection, any convenient plasmid vector may be used, preferably comprising a selectable expression vector and promoter. Suitable plasmids include pc DNA3 (Invitrogen), pCI (Promega), pCMV-beta galactosidase (Clontech) or pRc/CMV-HBs (S) Davis et al. Human Molecular Genetics 2:1847-1851. The ALS gene is inserted in the vector in any convenient manner. The gene may be obtained from Candida genomic DNA and amplified using PCR and the PCR product cloned into the vector. The ALS gene plasmid may be transferred, such as by electroporation, into E. coli for replication therein. Plasmids may be extracted from the E. coli in any convenient manner.

The plasmid containing the ALS gene or specified N-terminal fragment may be administered in any convenient manner to the host, such as intramuscularly, intranasally, intramusonally, intraperitoneally, transdermally or any selected route that elicits the immune response. DNA immunization with the ALS gene or fragment may elicit both cellular and humoral immune responses and produces significant protective immunity and therapeutic effect to Candida albicans.

As noted above, the ALS gene, gene product or specific antibodies may be mixed with pharmaceutically acceptable excipients which are compatible therewith. Such excipients may include, water, saline, dextrose, glycerol, ethanol, and combinations thereof. The immunogenic compositions and vaccines may further contain auxiliary substances, such as wetting or emulsifying agents, pH buffering agents, or adjuvants to enhance the effectiveness thereof. Immunogenic compositions and passive vaccines may be administered parenterally, by injection subcutaneously, intravenously, intradermally or intramuscularly, possibly following pretreatment of the injection site with a local anesthetic. Alternatively, the immunogenic compositions formed according to the present invention, may be formulated and delivered in a manner to evoke an immune response at mucosal surfaces. Thus, the immunogenic composition may be administered to mucosal surfaces by, for example, the nasal or oral (intragastric) routes. Alternatively, other modes of administration including suppositories and oral formulations may be desirable. For suppositories, binders and carriers may include, for example, polyalkylene glycols or triglycerides. Oral formulations may include normally employed incipients, such as, for example, pharmaceutical grades of saccharine, cellulose and magnesium carbonate.

The immunogenic preparations and vaccines are administered in a manner compatible with the dosage formulation, and in such amount as will be therapeutically effective, protective and immunogenic. The quantity to be administered depends on the subject to be treated, including, for example, the capacity of the individual's immune system to synthesize the ALS polypeptide or fragment thereof, and antibodies thereto, and if needed, to produce a humoral or cell-mediated immune response. Suitable dosage ranges are readily determinable by one skilled in the art and may be of the order of about 1 microgram to about 1 mg. Suitable regimes for initial administration and booster doses are also variable, but may include an initial administration followed by subsequent administrations. The dosage may also depend on the route of administration and will vary according to the size of the host. A vaccine which protects against only one pathogen is a monovalent vaccine. Vaccines which contain antigenic material of several pathogens are combined vaccines and also belong to the present invention. Such combined vaccines contain, for example, material from various pathogens or from various strains of the same pathogen, or from combinations of various pathogens.

Immunogenicity can be significantly improved if immunogens are co-administered with adjuvants, commonly used as 0.05 to 0.1 percent solution in phosphate-buffered saline. Adjuvants enhance the immunogenicity of an antigen but are not necessarily immunogenic themselves. Adjuvants may act by retaining the immunogen locally near the site of administration to produce a depot effect facilitating a slow, sustained release of antigen to cells of the immune system. Adjuvants can also attract cells of the immune system to the immunogen and stimulate such cells to elicit immune responses.

Immunostimulatory agents or adjuvants have been used for many years to improve the host immune responses to vaccines. Thus, adjuvants have been identified that enhance the immune response to antigens. Some of these adjuvants are toxic, however, and can cause undesirable side-effects, making them unsuitable for use in humans and many animals. Indeed, only aluminum hydroxide and aluminum phosphate (collectively commonly referred to as alum) are routinely used as adjuvants in human and veterinary vaccines.

A wide range of extrinsic adjuvants and other immunomodulating material can provoke potent immune responses to antigens. These include saponins complexed to membrane protein antigens to produce immune stimulating complexes (ISCOMS), pluronic polymers with mineral oil, killed mycobacteria in mineral oil, Freund's complete adjuvant, bacterial products, such as muramyl dipeptide (MDP) and lipopolysaccharide (LPS), as well as monophoryl lipid A, QS 21 and polyphosphazene.

The particular examples set forth herein are instructional and should not be interpreted as limitations on the applications to which those of ordinary skill are able to apply this invention. Modifications and other uses are available to those skilled in the art which are encompassed within the spirit and scope of the following claims. 

We claim:
 1. A method of vaccinating a mammalian host against Candida albicans comprising administering to said host a pharmacologically effective amount of an immunogenic composition comprising an isolated polypeptide consisting of the N-terminal domain of the Candida albicans agglutinin like sequence (ALS) polypeptide, Als3p, in a pharmacologically acceptable excipient, wherein the N-terminal domain extends from the end of the signal peptide for the beginning of the tandem repeat of said Candida albicans Als3p, and wherein the method inhibits adhesion of the Candida albicans to endothelial cells in said host.
 2. The method of claim 1, wherein said method comprises administering the immunogenic composition subcutaneously to said mammalian host.
 3. The method of claim 1, wherein the polypeptide is substantially pure.
 4. The method of claim 1, wherein the immunogenic composition comprises an immunostimulating adjuvant.
 5. The method of claim 4, wherein the immunostimulating adjuvant is alum.
 6. The method of any one of claims 2, 4 and 5, wherein said immunogenic composition is administered to the mammalian host as a booster dose.
 7. The method of claim 1, wherein the polypeptide is produced in Saccharomyces cerevisiae.
 8. The method of claim 1, wherein the mammalian host is a human and said polypeptide is purified.
 9. The method of claim 1, wherein the Als3p has the amino acid sequence set forth in SEQ ID NO:
 12. 